对Bitmap放大缩小处理与裁剪

示例效果图

如下图所示，把拿到的招商银行的图标做成右侧半透明的不规则形状的背景

实现方法

1、带弧度的圆角矩形和图片透明度

由于这张图的白色背景部分是一个圆角矩形带阴影的背景图片，所以要注意放上去的图标不要遮住圆角和阴影，需要一个圆角矩形的ImageView的控件，圆角的弧度和白色背景的圆角弧度一致。圆角矩形ImageView，弧度可以自己调节

public class XCRoundRectImageView extends ImageView {

    private Paint paint;
    
    public XCRoundRectImageView(Context context) {
        this(context,null);  
    }  
  
    public XCRoundRectImageView(Context context, AttributeSet attrs) {
        this(context, attrs,0);  
    }  
  
    public XCRoundRectImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle); 
        paint  = new Paint();
    }  
  
    /**
     * 绘制圆角矩形图片
     * @author caizhiming
     */
    @Override
    protected void onDraw(Canvas canvas) {
  
        Drawable drawable = getDrawable();
        if (null != drawable) {  
            Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
            Bitmap b = getRoundBitmap(bitmap, 25);
            final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
            final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
            paint.reset();  
            canvas.drawBitmap(b, rectSrc, rectDest, paint);  
  
        } else {  
            super.onDraw(canvas);  
        }  
    }  
  
    /**
     * 获取圆角矩形图片方法
     * @param bitmap
     * @param roundPx,一般设置成14
     * @return Bitmap
     * @author caizhiming
     */
    private Bitmap getRoundBitmap(Bitmap bitmap, int roundPx) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
          
        final int color = 0xff424242;
       
        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        final RectF rectF = new RectF(rect);
        paint.setAntiAlias(true);  
        canvas.drawARGB(0, 0, 0, 0);  
        paint.setColor(color);  
        int x = bitmap.getWidth(); 
        
        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);  
        return output;  
        
        
    }  
}  

使用，背景图标需要一定的透明度，设置 android:alpha=“0.06”

     <com.basestonedata.instalment.ui.scanpay.wiget.XCRoundRectImageView
            android:id="@+id/iv_bg_logo"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_alignParentBottom="true"
            android:scaleType="centerInside"
            android:layout_marginRight="10dp"
            android:layout_marginBottom="5dp"
            android:layout_marginTop="10dp"
            android:alpha="0.06" />

2、把图片资源或者图片链接变成bitmap

把资源文件中的图片转化为bitmap

Resources res = MainActivity.this.getResources();
Bitmap bmp= BitmapFactory.decodeResource(res, R.mipmap.flower);

把Url图片链接转化为bitmap

//ImageLoader
Bitmap bitmap = ImageLoader.getInstance().loadImageSync((url),options);

//Glide框架
 Glide.with(getActivity()).load(mUserEntity.getData().getCover()).asBitmap().into(new SimpleTarget<Bitmap>() {
            @Override
            public void onResourceReady(Bitmap resource, GlideAnimation<? super Bitmap> glideAnimation) {
                bitmap = resource;
            }
        });

3、图片的放大与裁剪处理

public class BitmapCropUtils {

//放大图片 新的宽高dp，放大缩小
    public static Bitmap zoomImg(Context context, Bitmap bm, int newWidth , int newHeight){
        // 获得图片的宽高
        int width = bm.getWidth();
        int height = bm.getHeight();
        // 计算缩放比例
        float scaleWidth = ((float) dip2px(context,newWidth)) / width;
        float scaleHeight = ((float) dip2px(context,newHeight)) / height;
        // 取得想要缩放的matrix参数
        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        // 得到新的图片
        Bitmap newbm = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, true);
        Bitmap returnBm=imageCrop(context,newbm);
        return returnBm;
    }

//裁剪图片
    public  static Bitmap imageCrop(Context context, Bitmap bitmap) {
        // 得到图片的宽，高
        int w = bitmap.getWidth();
        int h = bitmap.getHeight();

       //width最大不能超过长方形的短边
        if (w < width || h < width) {
           width = w > h ? h : w;
        }

//可以从图片的中心裁剪
//        int retX = (w - width) / 2;
//        int retY = (h - width) / 2;

       //public static Bitmap createBitmap (Bitmap source, int x, int y, int width, int height, Matrix m, boolean filter)
       // surce：用来剪裁的图片源;
       // x：剪裁x方向的起始位置;
       //y：剪裁y方向的起始位置;
       //width：剪裁的宽度;
       //height：剪裁的高度;
       //filer：不是很清楚它的作用 - -！
       //需要注意的是：必须满足条件：x+width<=bitmap.width()（图片源的原始宽度）否则会抛出IllegalArgumentException异常。
        return Bitmap.createBitmap(bitmap, 0, 0,dip2px(context,145), dip2px(context,125), null, false);
    }

//把图片裁剪成圆形（补充）
  public static Bitmap getCircleBitmap(Bitmap bitmap) {
        if (bitmap == null) {
            return null;
        }
        bitmap = cropBitmap(bitmap);//裁剪成正方形
        try {
            Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(),
                    bitmap.getHeight(), Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(circleBitmap);
            final Paint paint = new Paint();
            final Rect rect = new Rect(0, 0, bitmap.getWidth(),
                    bitmap.getHeight());
            final RectF rectF = new RectF(new Rect(0, 0, bitmap.getWidth(),
                    bitmap.getHeight()));
            float roundPx = 0.0f;
            roundPx = bitmap.getWidth();
            paint.setAntiAlias(true);
            canvas.drawARGB(0, 0, 0, 0);
            paint.setColor(Color.WHITE);
            canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
            final Rect src = new Rect(0, 0, bitmap.getWidth(),
                    bitmap.getHeight());
            canvas.drawBitmap(bitmap, src, rect, paint);
            return circleBitmap;
        } catch (Exception e) {
            return bitmap;
        }
    }

    /**
     * 根据手机的分辨率从 dp 的单位 转成为 px(像素)
     */
    public static int dip2px(Context context, float dpValue) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }
}